This document describes a method to produce a dynamic sound stage for engine harmonic enhancement (EHE). Dynamic refers to the ability to position the sound stage at different positions as the engine operates at various RPMs and load.
Engine harmonic enhancement (EHE) is used to create a set of harmonic signals to complement or mask certain characteristics of an engine sound. Each harmonic signal generated in EHE, has a magnitude, ck(t), and phase, φk(t), that varies in time:kk(t)=ck(t)·sin(ωk(t)·t+ωk(t))  (1)
where
            ω      k        =                  2        ⁢                                  ⁢        π        ⁢                                  ⁢                  f          k                    =                        2          ⁢                                          ⁢          π          ⁢                                          ⁢                      l            k                    ⁢                                          ⁢                      f            1                          =                  2          ⁢                                          ⁢          π          ⁢                                          ⁢                      l            k                    ⁢                      RPM            60                                ,and f1 is the fundamental frequency of the engine, lk is the harmonic order that usually is a multiple of 0.5, but in general, from an algorithm capability, can be a positive non-zero real number. RPM is the engine speed, and fk is the frequency, in Hz, of harmonic k.hk(t)=ck(rpm(t))·sin(ωk(rpm(t))·t+ωk(rpm(t)))  (2)
The signal generated in EHE is a function of time, RPM, engine load, and can be written as the sum of all contributing harmonics:x(rpm,t)=Σk=1Nck(rpm)·sin(ωk(rpm)·t+ωk(rpm))  (3)
where N is a total number of harmonics considered.